Voyager 1 might have seen Enceladus’ icy plumes 25 years early

Voyager 1 looked back at Saturn on Nov. 16, 1980, four days after the spacecraft flew past the planet

NASA/JPL

By Will Gater

We could have spotted the majestic icy plumes of Saturn’s moon Enceladus 25 years earlier than we did, if only we’d known to look.

The vast fountains of icy material erupting from Enceladus’s south pole enthralled planetary scientists when they were first spotted in images returned by NASA’s Cassini spacecraft in 2005. Further observations suggest that the moon hosts a subsurface sea that could be one of the best places in the solar system to look for life.

Now a space image-processing enthusiast from Tennessee, in the US, believes he’s made a ‘pre-discovery’ of those plumes in archive image data from the Voyager 1 probe, which raced past the Saturn system in 1980.

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Ted Stryk – an associate professor of philosophy and English at Roane State Community College who has recently worked with the NASA New Horizons team – processed Voyager 1 data that is publicly available from NASA’s online Planetary Data System to reveal a faint protrusion emanating from the frozen moon’s southern hemisphere.

Stacking images

In order to spot Enceladus’ plumes in the old Voyager data, Stryk needed images taken when the moon was illuminated at a certain angle. But the probe didn’t capture any deliberately targeted shots at those key moments.

So he had to search the archive for where the moon cropped up, under those conditions, in Voyager 1 pictures of other Saturnian subjects. “There was one set where there was a series of eight images that contained Enceladus, just a few pixels across, at a not optimal but useful phase-angle for this kind of work,” he says.

Enceladus in the distance

NASA / JPL-Caltech / Ted Stryk

By stacking together and averaging those images, taken in November of 1980, Stryk was able to boost the signal-to-noise ratio of the final picture and so reveal the feature he argues are the plumes found by Cassini decades later. Stryk’s work will be published in the proceedings of the Lunar and Planetary Science Conference, which will take place in The Woodlands, Texas next month.

Plumes in view?

NASA / JPL-Caltech / Ted Stryk

“It’s remarkable to be able to go back to data taken almost a quarter of a century before Cassini arrived and, armed with the discovery information from Cassini, produce this remarkable processed Voyager image which seems to reveal the plume at that time,” says Andrew Coates, a Cassini scientist at the Mullard Space Science Laboratory in the UK.

If Stryk’s processed image does indeed show the plume from Enceladus’ jets, that could supply researchers with an intriguing new data point, he adds.

“Another detection from 1980 if confirmed has the potential, once the data are fully understood and calibrated, to tell us something about how long the activity has been going on for.”